Nitric oxide (NO) plays important roles in myriad biological processes and is considered as a biomarker of cardiovascular disease, hypertension, symptoms of vaginitis, and cancer. Sensitive detection of NO molecules is vital toward the understanding of cell functionality and pathology as well as to the diagnosis of disease, drug discovery, and biological research [1-4]. Here, we report on the development of high-performance NO electrochemical sensors based on the nanocomposite of reduced graphene oxide (rGO) and AuPt bimetallic nanoparticles (rGO-AuPt) and the nanoporous Au microelectrode.

The rGO-AuPt nanocomposites were formed a glassy carbon electrode (GCE) using an electrochemical method. The prepared nanocomposites were tested for the electrochemical detection of NO using differential pulse voltammetry (DPV) and amperometric methods. The dependence of AuPt molar ratios on the electrochemical performance was investigated. Through the combination of the advantages of the high conductivity from rGO and highly electrocatalytic activity from AuPt bimetallic nanoparticles, the rGO-AuPt based NO sensor exhibited a high sensitivity of 7.35 µA µM^-1 and a low detection limit of 2.88 nM. Additionally, negligible interference from common ions or organic molecules was observed, and the r-GO-AuPt modified electrode demonstrated excellent stability. Moreover, this optimized electrochemical sensor was practicable for efficiently monitoring the NO released from rat cardiac cells, which were stimulated by L-arginine (L-arg), showing that stressed cells generated over 10 times more NO than normal cells.

The nanoporous gold microelectrode was fabricated via an electrochemical alloying/dealloying method. It exhibited a high electrochemically active surface area and excellent performance for the detection of NO with high stability. Based on DPV and amperometric techniques, extremely high sensitivities (21.9 μA μM^-1 cm^-2 and 14.3 μA μM^-1 cm^-2) with very low detection limits of 17.0 nM and 1.43 nM, respectively, have been achieved. Moreover, the developed nanoporous Au microelectrode provides a new approach to monitor NO release from different cells, revealing that a significant differential amount of NO can be generated from the normal and stressed rat cardiac cells as well as from the untreated and treated breast cancer cells, promising for the elucidation of cellular stress responses and medical diagnostics.

References

[1] Z.G. Liu, H. Forsyth, N.Khaper, A. Chen. Analyst 141 (2016) 4074-4083.

[2] M. Govindhan, A. Chen. Microchim. Acta 183 (2016) 2879-2887

[3] M. Govindhan, Z. Liu, A. Chen. Nanomater. 6 (2016) 211.

[4] Z Liu, A Nemec-Bakk, N Khaper, A Chen. Anal. Chem. 89 (2017) 8036-8043